In the manufacture of mineral fiber from molten material, it has been common practice to apply a liquid size to the fiber as the fiber moves rapidly, at least 1000 feet per minute and usually much faster from the fiberizing bushing towards a turning or pad wheel. The liquid sizing, that can be any one of many available to tailor the fiber for particular applications, usually contains one or more film formers to protect the fiber and hold the sizing together, one or more lubricants to protect the fiber from abrasion and to reduce friction and one or more linking agents that promote bonds between the surface of the fiber and the film former and/or the matrix or binder that will surround the fiber at a later time in any one of thousands of applications. Many applicators are known for applying sizing such as those disclosed in U.S. Pat. Nos. 6,592,666, 6,818,065.
Prior art applicators have one or more shortcomings that the present invention addresses. One shortcoming is that of maintaining a reservoir of sizing in a lower portion of the applicator. The temperature in the forming room is often above room temperature and the sizing applicators are exposed to radiant heat from the red-yellow hot bushings. This causes sizing that sets in a reservoir for various lengths of time to degrade and to form higher viscosity and/or globules. Also, dust, foreign particles and pieces of fiber often come in contact with the element of the applicator that contacts the fiber that is being sized. These dust and fiber particles and segments then get washed off into the sizing that is in the reservoir and is then reapplied to the applicator element, such as a roll or a belt. The presence of high viscosity sizing, globules of sizing, foreign particles and pieces and/or segments of fiber on then fiber contacting element of the applicator cause fiber breaks, incomplete sizing of the fiber and undesirable sizing content variation in the finished fiber product. These problems with prior sizing applicators have been made worse, more frequent and more costly, as more fibers are pulled from a bushing necessitating that the applicator be larger, wider to accommodate the wider fan or array of fibers thus making it easier for foreign matter to collect on the applicator element and get into the sizing and providing more surface area for radiant heating from the bushings. Bushings today typically produce 3000 or more fibers and often produce 4000-7,000-8000 fibers, particularly when making chopped fiber products.
The above conditions pertain to the sizing of fibers made from any molten material and are most costly in the manufacture of so-called “continuous” glass fiber products made from molten glass. In the manufacture of continuous glass fibers, melting furnaces are typically used to melt batch, refine the molten glass, and to feed molten glass through one or more forehearths and usually a plurality of bushing legs to the bushings. The bushings are maintained at a temperature that is in the red to yellow heat range for glass. Typically hundreds to thousands of fibers are pulled at speeds up to more than 100 miles per hour from molten beads, meniscus, of glass that form at the end of each hollow nozzle or orifice on the bottom of the bushing. The fibers are rapidly cooled and in fractions of a second are brought into contact with the fiber coating element (element of the applicator that carries the sizing to the fiber) of the applicator, usually a curved surface, a roller or a belt. A layer of sizing exists on the surface of the coating element of the applicator, continuous layer when working properly, but often discontinuous due to conditions mentioned above. The rapidly moving fiber is in contact with the element and layer of sizing for only microseconds and if a portion of the element is not coated with sizing the fiber coming in contact with that portion will either break, not get coated with sizing or not receive enough sizing.
When one or more fiber choppers are present in the fiber forming room, which is normal due to the large amount of chopped fiber produced to make nonwoven mats and other chopped fiber products, the amount of fiber particles, backup roll particles, and fiber segments in the air is greatly increased.
When a fiber breaks, all of the fibers coming from the same bushing soon break out. Many seconds are then required for the bushing to “bead out” and to be producing primary, coarse fibers from each nozzle. At that time the bushing can be restarted by the operator or a machine taking all or most of the primary fibers to the chopper and inserting them into the chopper. If the operator is busy with another task, the bushing continues to be out of production until the operator is able to restart the bushing. The longer the bushing is “hanging”, the more the system deviates from optimum fiberizing conditions and this causes further fiber breaks, with the “hanging bushing” and bushings downstream in a same bushing leg. It is well established that the higher the rate of fiber breaks of a bushing, a leg of bushings and of an entire forming room, the greater the variation of the fiber diameter and the LOI, sizing content, of the fiber products being produced.
The present invention addresses these shortcomings of prior art sizing applicators to reduce fiber break rate, reduce manufacturing costs, and to improve both productivity and product quality.